1. Field of Invention
The present invention relates to a water treatment apparatus and, more particularly, to a self-cleaning water treatment apparatus.
2. Related Prior Art
A conventional water treatment apparatus includes a filtering unit with a helically wound filtering film for filtering sludge out of water. To increase an effective area of the filtering unit for intercepting the sludge to increase the throughput of the production of filtered water, flat filtering bags are now used instead of the helically wound filtering film. The flat filtering bags are located along and around a filtered-water pipe. There is no need to provide a rigid shell to close the flat filtering bags. The flat filtering bags are simply located between two plates. Therefore, the effective area of the filtering unit for intercepting sludge is large. The size of the filtering unit consisting of the flat filtering bags is small. Advantageously, unfiltered water travels over the flat filtering bags at high speed and the throughput of the production of the filtered water is high. A water jet is used to wash the sludge away from external faces of the flat filtering bags.
To suppress the forming of filter cakes on the external faces of the flat filtering bags, air is pumped into the water treatment apparatus to increase stirring of the unfiltered water over the external faces of the flat filtering bags. Moreover, the flat filtering bags are spun. Thus, the external faces of the flat filtering bags are moved relative to the unfiltered water. The sludge and particles are removed from the external faces of the flat filtering bags. Hence, the flat filtering bags are not blocked. The throughput of the production of the filtered water is not reduced rapidly. Details of this technique can be found in Taiwanese Patent I312767 for example.
There are various sources of unfiltered water including various undesired substances such as floc, solids and grease used to facilitate cutting. Where the flat filtering bags are used to treat unfiltered water including a lot of grease, the grease sticks the external faces of the flat filtering bags and affects the throughput of the production of the filtered water. Even worse, it is difficult to wash the grease away from the external faces of the flat filtering bags with a water jet. The life of the flat filtering bags is reduced.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.